Everybody knows driving under the influence of alcohol is dangerous. More recently, Australian police started testing drivers for drugs that are known to adversely affect their driving. Now a recent US study finds drivers with a combination of alcohol and marijuana in their body are five times more likely than sober drivers to cause fatal two-car crashes.

The study

The study investigated over 14,000 at-fault drivers and over 14,000 not at-fault drivers in the same crashes between 1993 and 2014. Results showed:

Alcohol on its own increases crash likelihood by 437% (just over 4 times)

Marijuana on its own increases it by 62% (just under two thirds)

Alcohol plus marijuana increases crash likelihood by over 5 times.

The most common at-fault driver with both alcohol and marijuana readings was male, 25-44 with a history of violations and crashes in the previous 3 years. Their most common fatal errors were:

Failure to stay in the right lane (43%)

Failure to give right of way (22%)

Speeding (21%).

Results like this help explain why mobile drug testing has been introduced.

Mobile drug testing

The NSW government began mobile drug testing (MDT) and random breath testing (RBT) some time ago. As with RBT, drivers who are stopped for MDT must still do a breath test for alcohol.

If stopped, police test drivers for the presence in their body of ecstasy, cannabis and speed (including ice) and just announced, cocaine. Penalties for an offence depend on whether it is classified as presence or driving under the influence.

In 2015, 10% of MDTs came back positive, compared to less than 1% of RBTs for alcohol. In fact, over 2 years to June 2016, the number of drug driving charges finalised in court increased by 320% (BITRE figures).

Average offender

The average drug driving offender in NSW is similar to the one in the US study: young, male, 18-39. They are twice as likely to be driving in regional NSW than in the city. For example, the highest rates of prosecuted drug driving are in:

Richmond-Tweed – 0.47%

Sydney Outer South West – 0.33%

Riverina – 0.32%

These rates compare with the NSW average of 0.09%. Offenders were least likely to be in Ryde (0.007%), followed by North Sydney/Hornsby (0.01%). The full list (available from BITRE) seems to show the people least able to afford illegal drugs are the ones most likely to get caught drug driving.

Your green slip

Insurers ask about at-fault accidents in the last 2 years and driving convictions or licence suspensions in the last 5 years. Driving with alcohol or drugs (or both) is not only dangerous for everyone – and a crime – but guarantees the price of your green slip will rocket.

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Corrina Baird

Writer and expert greenslips.com.au

Corrina used to lend her car to her kids and discovered first hand what Ls, Ps and demerits mean for greenslips. After 20 years of writing and research in financial services, she’s an expert in the NSW CTP scheme.
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